Rogue planet astounds by growing at a record rate of 6 billion tonnes per second
These starless worlds are difficult to find and study, but this particular one is teaching us new lessons about the universe.
A young alien planet, wandering alone in the galaxy, has surprised astronomers by gobbling up gas and dust at a rate faster than they've ever seen before.
Throughout the Milky Way, there are potentially billions of planets floating freely, unbound from any of the stars in the galaxy. Many of these 'rogue planets' likely formed in a star system, but then some unfortunate gravitational encounter flung them away fast enough that they were ejected into interstellar space. However, just as many, if not more, of these worlds may have formed in the space between stars, resulting from the gravitational collapse of a small cloud of gas and dust.
Rogue planets are difficult to spot, as they only emit a small amount of light compared to stars. Still, up to 170 have been detected so far, with possibly hundreds of candidates waiting to be confirmed.
One rogue planet in particular, named Cha 1107-7626, recently caught the attention of astronomers. Located about 620 light years away, in the southern constellation Chamaeleon, this young rogue planet is already anywhere from five to ten times the mass of Jupiter. Also, thanks to the disk of dust and gas that surrounds it, it is still growing!
This illustration shows rogue planet Cha 1107-7626 consuming matter from the disk of gas and dust that surrounds it. (ESO/L. Calçada/M. Kornmesser)
By observing Cha 1107-7626 over time, a team of researchers tracked how quickly the planet was accumulating matter from its disk, and discovered that the rate wasn't constant.
In fact, in August of this year, it was accreting matter around 8 times faster than it was just a few months before, back in May. Its rate of consumption topped out at around six billion metric tons every second!
"This is the strongest accretion episode ever recorded for a planetary-mass object," Víctor Almendros-Abad, an astronomer at the Astronomical Observatory of Palermo, in Italy, said in a ESO press release.
This closer view of Cha 1107-7626 shows the intense bright region in the rogue planet's cloud layers caused by its magnetic field drawing in material from the disk around it. The increase in the rogue planet's brightness, caused by these spots, was what alerted astronomers to its rapid rate of consumption. (ESO/L. Calçada/M. Kornmesser)
"People may think of planets as quiet and stable worlds, but with this discovery we see that planetary-mass objects freely floating in space can be exciting places," Almendros-Abad explained.
Combining observations with the X-shooter spectrograph on ESO’s Very Large Telescope, the James Webb Space Telescope, and past data gathered with the SINFONI spectrograph on VLT, Almendros-Abad and his colleagues used the brightness of Cha 1107-7626 to determine how quickly it was accreting matter.
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Planetary size, Stellar behaviour
In a rather bizarre twist, by observing this dramatic increase in accretion, it turns out that they actually caught Cha 1107-7626 displaying some very star-like behaviour.
This included the planet's magnetic field playing a role in how quickly it accreted matter, something that was thought only to occur with stellar-mass objects. Plus, they also detected chemical changes in the disk around Cha 1107-7626, resulting in the production of both hydrocarbons and water.
"When we examined the data, we didn't expect such a dramatic result," Almendros Abad said in an Astronomical Observatory of Palermo press release. "The James Webb data showed us that the chemistry of the protoplanetary disk changed due to the accretion of material, a phenomenon that had previously only been observed in a few stars."
Three views of rogue planet Cha 1107-7626 reveal its rapid consumption of gas and dust from the disk around it, helped along by the planet's powerful magnetic field drawing loops of material in at an accelerated rate. (ESO/L. Calçada/M. Kornmesser)
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"This discovery blurs the line between stars and planets and gives us a sneak peek into the earliest formation periods of rogue planets," co-author Belinda Damian, an astronomer at the University of St Andrews, told the ESO.
"The idea that a planetary object can behave like a star is awe-inspiring and invites us to wonder what worlds beyond our own could be like during their nascent stages," added co-author Amelia Bayo, an astronomer at the European Southern Observatory.
Two upcoming telescopes could revolutionize rogue planet astronomy, by detecting more of them than any other observatory so far.
An artist's impression of the Nancy Grace Roman Space Telescope. (NASA's Goddard Space Flight Center Scientific Visualization Studio)
The first is NASA’s Nancy Grace Roman Space Telescope. Currently set to launch in May 2027, it will use a field of view 100 times larger than Hubble’s to study dark energy, exoplanets, and astrophysics.
Its sensitivity will also allow astronomers to detect many more rogue planets travelling through interstellar space.
A simulated look at the Extremely Large Telescope, when it is completed in the coming years. (ESO)
The next after that is the upcoming Extremely Large Telescope (ELT), currently being built by the ESO atop Cerro Armazones in northern Chile.
This ground-based observatory will be the largest optical telescope on Earth, with a primary mirror nearly 40 metres across, and is expected to see First Light sometime in 2029.